Compact antenna designs have become a critical component in the recent advancements of wireless communication technologies over the past few decades. This paper presents a self-multiplexing antenna based on diplexing ...Compact antenna designs have become a critical component in the recent advancements of wireless communication technologies over the past few decades. This paper presents a self-multiplexing antenna based on diplexing and quadruplexing Substrate-Integrated Waveguide (SIW) cavities. The diplexing structure incorporates two V-shaped slots, while the quadruplexing structure advances this concept by combining the slots to form a cross-shaped configuration within the cavity. The widths and lengths of the slots are carefully tuned to achieve variations in the respective operating frequencies without affecting the others. The proposed diplexing antenna resonates at 8.48 and 9.2 GHz, with a frequency ratio of 1.08, while the quadruplexing antenna operates at 6.9, 7.1, 7.48, and 8.2GHz. Both designs exhibit isolation levels well below –20dB and achieve a simulated peak gain of 5.6 dBi at the highest frequency, with a compact cavity area of 0.56 λg^(2). The proposed antennas operate within the NR bands (n12, n18, n26), making them suitable for modern high-speed wireless communication systems. Moreover, the properties like multiband operation, compactness, high isolation, low loss, and low interference make the antenna favorable for the high-speed railway communication systems.展开更多
In the current study the wear behavior of the ZK60/SiC composites reinforced by particles and whiskers in both as-cast and extruded conditions was examined.Furthermore,the wear behavior of the extruded samples along t...In the current study the wear behavior of the ZK60/SiC composites reinforced by particles and whiskers in both as-cast and extruded conditions was examined.Furthermore,the wear behavior of the extruded samples along the extrusion direction and perpendicular to the extrusion direction was studied.The wear tests were performed at temperatures of 100,200,and 300℃under loads of 10,20,and 30 N.The results showed that the whisker-reinforced sample(5.8×10^(–4)g/[N.m])had higher wear resistance than the particle-reinforced sample(1.3×10^(–3)g/[N.m]).The lowest wear rate was observed for the extruded sample in the extrusion direction(3.53×10^(–4)g/[N.m]).It was also found that the wear rate increased by∼20%with increasing temperature,but in the ZK60/SiC_(w)sample,dynamic precipitation increased the wear resistance.The coefficient of friction was also found to increase with rising temperature,showing an increase of approximately 12.5%at a 10 N load and 20%at a 30 N load.Examination of the worn surfaces by scanning electron microscopy showed that the as-cast ZK60 alloy at 100℃had the oxidative-abrasive as the dominant mechanism.It was found that by extruding the sample,the strength of the sample increased and the mechanism changed to adhesive wear.In the ZK60/SiC_(p)composite,the viscoplastic wear mechanism was dominant.Although in the extruded sample the dominant mechanism changed to plastic deformation.As temperature increases,the viscoplastic wear mechanism became dominant again.In the as-cast ZK60/SiC_(w)composite,the abrasive wear mechanism changed to delamination with increasing temperature.By extruding the sample,the dominant mechanism changed to adhesive wear.Finally,dynamic precipitation induced by temperature caused an increase in the wear resistance.展开更多
This article presents a compact crab-shaped reconfigurable antenna(CSRA)designed for 5G sub-6 GHz wireless applications. The antenna achieves enhanced gain in a miniaturized form factor by incorporating a hexagonal sp...This article presents a compact crab-shaped reconfigurable antenna(CSRA)designed for 5G sub-6 GHz wireless applications. The antenna achieves enhanced gain in a miniaturized form factor by incorporating a hexagonal split-ring structure controlled via two radio frequency(RF) positive-intrinsicnegative(PIN) diodes(BAR64-02V). While the antenna is primarily designed to operate at 3.50 GHz for sub-6 GHz 5G applications, RF switching enables the CSRA to cover a broader frequency spectrum, including the S-band, X-band, and portions of the Ku-band. The proposed antenna offers several advantages: It is low-cost(fabricated on an FR-4 substrate), compact(achieving 64.07% size reduction compared to conventional designs), and features both frequency and gain reconfigurability through digitally controlled PIN diode switching. The reflection coefficients of the antenna, both without diodes and across all four switching states, were experimentally validated in the laboratory using a Keysight Field Fox microwave analyzer(N9916A, 14 GHz). The simulated radiation patterns and gain characteristics closely matched the measured values, demonstrating an excellent agreement. This study bridges the gap between traditional and next-generation antenna designs by offering a compact,cost-effective, and high-performance solution for multiband, reconfigurable wireless communication systems. The integration of double-split-ring resonators and dynamic reconfigurability makes the proposed antenna a strong candidate for various applications, including S-band and X-band systems, as well as the emerging lower 6G band(7.125 GHz–8.400 GHz).展开更多
Friction stir processing(FSP)induces severe plastic deformation,generating intense strains and localized heating,which modifies the surface and enables the fabrication of magnesium(Mg)-based composites.This technique ...Friction stir processing(FSP)induces severe plastic deformation,generating intense strains and localized heating,which modifies the surface and enables the fabrication of magnesium(Mg)-based composites.This technique refines the microstructure of Mg alloys,enhancing mechanical properties—particularly ductility,a key limitation of these HCP alloys.This review addresses the underlying microstructural evolution during FSP of Mg alloys and Mg-matrix composites,including(i)grain refinement via continuous and discontinuous dynamic recrystallization(CDRX and DDRX),(ii)fragmentation and redistribution of secondary phases and intermetallics,(iii)transformation of low-and high-angle grain boundaries,and(iv)additional microstructural changes induced by external reinforcements.This review provides a comprehensive analysis of the strengthening mechanisms and their impact on the mechanical properties of FSP Mg alloys and Mgmatrix composites(MMCs).The paper examines the correlation between FSP processing parameters,microstructural evolution,and resulting mechanical properties.It critically highlights how the type of reinforcement and the dynamic recrystallization induced by friction stir processing influence grain boundary character and,consequently,the material’s strengthening response.It includes a comparative evaluation of yield stress,ultimate tensile strength,microhardness,elongation,and fractography for various FSP-treated Mg alloys and MMCs,including AZxx,WExx,ZExx,ZKxx,AMxx,AExx,and Mg-rare earth alloys.Additionally,the novelty of this review lies in its emphasis on connecting microstructural transformations to mechanical performance trends across different alloy systems and processing strategies,an aspect that has been underexplored in previous reviews.Recent advancements in FSP techniques and their implications for improving the performance of Mg-based materials are also discussed.展开更多
This paper investigates the effects of material and dimension parameters on the frequency splitting,frequency drift,and quality factor(Q)of aluminium nitride(AlN)-on-n-doped/pure silicon(Si)microelectromechanical syst...This paper investigates the effects of material and dimension parameters on the frequency splitting,frequency drift,and quality factor(Q)of aluminium nitride(AlN)-on-n-doped/pure silicon(Si)microelectromechanical systems(MEMS)disk resonators through analysis and simulation.These parameters include the crystallographic orientation,dopant,substrate thickness,and temperature.The resonators operate in the elliptical,higher order,and flexural modes.The simulation results show that i)the turnover points of the resonators exist at 55°C,-50°C,40°C,and-10°C for n-doped silicon with the doping concentration of 2×1019 cm-3 and the Si thickness of 3.5μm,and these points are shifted with the substrate thickness and mode variations;ii)compared with pure Si,the modal-frequency splitting for n-doped Si is higher and increases from 5%to 10%for all studied modes;iii)Q of the resonators depends on the temperature and dopant.Therefore,the turnover,modal-frequency splitting,and Q of the resonators depend on the thickness and material of the substrate and the temperature.This work offers an analysis and design platform for high-performance MEMS gyroscopes as well as oscillators in terms of the temperature compensation by n-doped Si.展开更多
This paper proposes a simple solution for the stabilization of a mini-quadcopter carrying a 3DoF（degrees of freedom） manipulator robot in order to enhance its achievable workspace and application profile. Since the ...This paper proposes a simple solution for the stabilization of a mini-quadcopter carrying a 3DoF（degrees of freedom） manipulator robot in order to enhance its achievable workspace and application profile. Since the motion of the arm induces torques which degrade the stability of the system, in the present work, we consider the stabilization of both subsystems： the quadcopter and the robotic arm. The mathematical model of the system is based on quaternions. Likewise, an attitude control law consisting of a bounded quaternion-based feedback stabilizes the quadcopter to a desired attitude while the arm is evolving. The next stage is the translational dynamics which is simplified for control（nonlinear） design purposes. The aforementioned controllers are based on saturation functions whose stability is explicitly proved in the Lyapunov sense. Finally, experimental results and a statistical study validate the proposed control strategy.展开更多
Solid oxide fuel cells based on doped cefia electrolytes offer operating temperatures of -600℃. During recent years much atten- tion was aimed at successful powder preparation with high sinter activity and high condu...Solid oxide fuel cells based on doped cefia electrolytes offer operating temperatures of -600℃. During recent years much atten- tion was aimed at successful powder preparation with high sinter activity and high conductivity. The properties of ceria electrolyte are very sensitive to impurities introduced during powder and electrolyte fabrication. One of the most successful and commercially available processes for the production of clean powders is based on the addition of several percent metallic cations that will react with impurities and segregate into the triple points of grain boundaries. In this work the results obtained from doping of CGO20 by 2% Ca and prepared by different routes were presented. The way of introducing Ca seemed to play an important role.展开更多
Naturalfibre(NFR)reinforced functional polymer composites are quickly becoming an indispensable sustainable material in the transportation industry because of their lightweight,lower cost in manufacture,and adaptabilit...Naturalfibre(NFR)reinforced functional polymer composites are quickly becoming an indispensable sustainable material in the transportation industry because of their lightweight,lower cost in manufacture,and adaptability to a wide variety of goods.However,the major difficulties of using thesefibres are their existing poor dimensional stability and the extreme hydrophilicity.In assessing the mechanical properties(MP)of composites,the interfacial bonding(IB)happening between the NFR and the polymer matrix(PM)plays an incredibly significant role.When compared to NFR/syntheticfibre hybrid composites,hybrid composites(HC)made up of two separate NFR are less prevalent;yet,these hybrid composites also have the potential to be valuable materials in terms of environmental issues.A new dimension to theflexibility of composites reinforced with NFR is added by the cost-effective manufacture of hybrid composites utilising NFR.The purpose of this study is to offer an over-view of the keyfindings that were presented on hybrid composites.The emphasis was focused on the factors that influence the performance of the naturalfiber composites,diverse approaches to enhancing MP,physical,electri-cal,and thermal characteristics of the HC.HC study in polymer science gains interest for applications in con-struction and automotive industries.展开更多
This paper proposes an adaptive nonlinear proportional-derivative(ANPD)controller for a two-wheeled self-balancing robot(TWSB)modeled by the Lagrange equation with external forces.The proposed control scheme is design...This paper proposes an adaptive nonlinear proportional-derivative(ANPD)controller for a two-wheeled self-balancing robot(TWSB)modeled by the Lagrange equation with external forces.The proposed control scheme is designed based on the combination of a nonlinear proportional-derivative(NPD)controller and a genetic algorithm,in which the proportional-derivative(PD)parameters are updated online based on the tracking error and the preset error threshold.In addition,the genetic algorithm is employed to adaptively select initial controller parameters,contributing to system stability and improved control accuracy.The proposed controller is basic in design yet simple to implement.The ANPD controller has the advantage of being computationally lightweight and providing high robustness against external forces.The stability of the closed-loop system is rigorously analyzed and verified using Lyapunov theory,providing theoretical assurance of its robustness.Simulations and experimental results show that the TWSB robot with the proposed ANPD controller achieves quick balance and tracks target values with very small errors,demonstrating the effectiveness and performance of the proposed controller.The proposed ANPD controller demonstrates significant improvements in balancing and tracking performance for two-wheeled self-balancing robots,which has great applicability in the field of robot control systems.This represents a promising solution for applications requiring precise and stable motion control under varying external conditions.展开更多
Interference is a key factor in radar return misdetection.Strong interference might make it difficult to detect the signal or targets.When interference occurs in the sidelobes of the antenna pattern,Sidelobe Cancellat...Interference is a key factor in radar return misdetection.Strong interference might make it difficult to detect the signal or targets.When interference occurs in the sidelobes of the antenna pattern,Sidelobe Cancellation(SLC)and Sidelobe Blanking are two unique solutions to solve this problem(SLB).Aside from this approach,the probability of false alert and likelihood of detection are the most essential parameters in radar.The chance of a false alarm for any radar system should be minimal,and as a result,the probability of detection should be high.There are several interference cancellation strategies in the literature that are used to sustain consistent false alarms regardless of the clutter environment.With the necessity for interference cancellation methods and the constant false alarm rate(CFAR),the Maisel SLC algorithm has been modified to create a new algorithm for recognizing targets in the presence of severe interference.The received radar returns and interference are simulated as non-stationary in this approach,and side-lobe interference is cancelled using an adaptive algorithm.By comparing the performance of adaptive algorithms,simulation results are shown.In a severe clutter situation,the simulation results demonstrate a considerable increase in target recognition and signal to noise ratio when compared to the previous technique.展开更多
Recently, many studies propose the use of ultra-wideband technology for passive and active radio frequency identification systems as well as for wireless sensor networks due to its numerous advantages. By harvesting t...Recently, many studies propose the use of ultra-wideband technology for passive and active radio frequency identification systems as well as for wireless sensor networks due to its numerous advantages. By harvesting these advantages of IR-UWB technology at the physical-layer design, this paper proposes that a cross layer architecture platform can be considered as a good integrator for different wireless short-ranges indoor protocols into a universal smart wireless-tagged architecture with new promising applications in cognitive radio for future applications. Adaptive transmission algorithms have been studied to show the trade-off between different specific QoS requirements, transmission rates and distances at the physical layer level and this type of dynamic optimization and reconfiguration leads to the cross-layer design proposal in the paper. Studies from both theoretical simulation and statistical indoor environments experiments are considered as a proof of concept for the proposed architecture.展开更多
In this paper, a solution for electromagnetic compatibility guarantee based on the combination of metal shielding and circuit components distance estimation methods is presented. The electromagnetic noises generated f...In this paper, a solution for electromagnetic compatibility guarantee based on the combination of metal shielding and circuit components distance estimation methods is presented. The electromagnetic noises generated from a working radio-electronic unit can expand into the space and act on other around radio-electronic units. An EMC guaranteed radio-electronic unit by the suitable technique method will not cause the electromagnetic noise to others. In opposition, it will not be under electromagnetic action from another one. Due to the power of electromagnetic noise, the metal shielding, distance estimation or other technique methods should be used to guarantee EMC. Every method has own advantage as so as weakness for detail radio-electronic unit, so it is necessary to choose a suitable method to guarantee EMC for them, the combination of metal shielding and distance estimation is a choice, for example. The proposed solution has been evaluated by using CST (Computer Simulation Technology) software and EMxpertEHX analyzer in oscillator circuit context. The simulated results on CST show that the proposed solution decreases the electromagnetic radiation about of 39.1 dB at frequency 500 MHz in comparison to results when nothing electromagnetic compatibility methods are not used. The experimental results on the oscillator circuit are presented. The electromagnetic radiation reduction of the oscillator circuit is about of (25 - 30) dB. In comparison to individual metal shielding and distance estimation methods, the effectiveness of the proposed solution for electromagnetic compatibility guarantee is significantly increased.展开更多
This paper analyzes the possibility to discriminate between convective precipitation and stratiform precipitation. This study aims to improve the measurement of rainfall from teledetection data obtained both on the gr...This paper analyzes the possibility to discriminate between convective precipitation and stratiform precipitation. This study aims to improve the measurement of rainfall from teledetection data obtained both on the ground and in space. For this, two parameters, fractal dimension and fractal lacunarity, are considered. To calculate the fractal dimension, we use the approach of box-counting and show that the fractal dimension differs between convectives cells and stratiforms ones. And then the fractal lacunarity parameter is calculated by using the sliding boxes algorithm. The study for all the regions shows that precipitation cells can be described by different lacunarities whatever the scale of analysis. We deduce that the two parameters, fractal dimension and fractal lacunarity, can be used to classify precipitations in convective regime and stratiform regime.展开更多
In this paper,we propose a Two-Way Cognitive Relay Network(TWCRN)where the secondary users operate on an underlay mode to access the licensed bands.In the proposed protocols,two secondary sources transmit their data t...In this paper,we propose a Two-Way Cognitive Relay Network(TWCRN)where the secondary users operate on an underlay mode to access the licensed bands.In the proposed protocols,two secondary sources transmit their data to a relay in the first time slot,and then the relay would forward the received information to both sources in the remaining time.Moreover,the relay is self-powered by harvesting energy from ambient Radio Frequency(RF)signals,using the Time Switching(TS)and the Power Switching(PS)method.This paper concentrates on eval-uating the performance of the secondary networks under the impact of hardware impairments and co-channel interference from the primary networks.In particular,based on the secondary transmitters'constraint power,we derive the closed-form expressions of the outage probability and the throughput over Rayleigh fading channels in two cases:TS and PS.We also investigate the energy efficiency issue and the locally optimal position of the relay to maximize the system throughput,which provides much information to install the relay location.Finally,our derivations are verified by Monte Carlo simulation.展开更多
CIP （complex initial permeability） spectra of PF （polycrystalline ferrite） are studied both as intrinsic and extrinsic properties. In the former case, main steps of modeling, based on effects coming from polycryst...CIP （complex initial permeability） spectra of PF （polycrystalline ferrite） are studied both as intrinsic and extrinsic properties. In the former case, main steps of modeling, based on effects coming from polycrystal grain sizes distribution and defects, are described. The obtained relations work well in practice for PF with more or less normal MS （microstructure） and no size effects. Besides, fundamental connection between parameters of CIP and MS is found. Another case--PF with possible size effects （MnZn-ferrites） are studied experimentally for different sizes of cores, unveiling the dependence of phenomena on： dimensions of cross-section, number of turns, width of nonmagnetic gap.展开更多
Currently, the market offers many visualization tools available to graphic designers, engineers, managers and academics working on maritime environments. The practice of visualization involves making and manipulating ...Currently, the market offers many visualization tools available to graphic designers, engineers, managers and academics working on maritime environments. The practice of visualization involves making and manipulating images that convey novel phenomena and ideas. Visual communication, together with virtual reality environments, is an emerging and rapidly evolving discipline. It brings great advantage over written word or voice alone, as visual sense is by far the most dominant component of human sensory perception. A new smart approach for modeling maritime vessels is described in this paper. Various ways of making modeling relevant for work within the field of maritime management, training and education are discussed.展开更多
The paper discusses in a system view the security architecture of network layer of the Radio System for Monitoring and Acquisition of Data from Traffic Enforcement Cameras(in short RSMAD).The safety of this layer of t...The paper discusses in a system view the security architecture of network layer of the Radio System for Monitoring and Acquisition of Data from Traffic Enforcement Cameras(in short RSMAD).The safety of this layer of the system is provided basing primarily on Virtual Private Networks(in short VPN).Two protocols have been used for their implementation:IPsec(in tunnel mode of ESP protocol)and L2TP.Applied cryptography data protection mechanisms,including the type and parameters of the VPNs have been selected on the basis of carried out tests and measurements,which results are presented and discussed in this paper.The study presents also detailed comparative analysis in terms of performance AES-128 and Triple-DES algorithms carried out in RSMAD.展开更多
The authors＇ developed combined system model can be considered under the concept of next generation optical network （NGON） as a model for the future design of backbone networks. Such solution can be topical in the ...The authors＇ developed combined system model can be considered under the concept of next generation optical network （NGON） as a model for the future design of backbone networks. Such solution can be topical in the result of different telecom operators＇ optical networks convergence. In this case a necessity to transmit differently modulated signals over a single optical fiber even with different bit rates may occur. This research is performed with OptSim 5.2 simulation software that numerically solves nonlinear SchrOdinger equation. The authors have revealed the optimal parameter configuration for developed combined transmission systems and obtained in system＇s channels detected signals bit-error-rate （BER） correlation diagrams. They represent BER as a function from different system＇s parameters such as channel output power level, optical amplifier fixed output power level and system＇s channels allotment in C-band of ITU-T （Telecommunication Standardization Sector of the International Telecommunications Union） recommended spectral grid. As well as these obtained BER values were compared with the results for similar system, where instead of standard single mode fiber （according ITU-T Rec. G.652 D） optical signals are transmitted over non-zero dispersion shifted fiber （ITU-T Rec. G. 655）.展开更多
文摘Compact antenna designs have become a critical component in the recent advancements of wireless communication technologies over the past few decades. This paper presents a self-multiplexing antenna based on diplexing and quadruplexing Substrate-Integrated Waveguide (SIW) cavities. The diplexing structure incorporates two V-shaped slots, while the quadruplexing structure advances this concept by combining the slots to form a cross-shaped configuration within the cavity. The widths and lengths of the slots are carefully tuned to achieve variations in the respective operating frequencies without affecting the others. The proposed diplexing antenna resonates at 8.48 and 9.2 GHz, with a frequency ratio of 1.08, while the quadruplexing antenna operates at 6.9, 7.1, 7.48, and 8.2GHz. Both designs exhibit isolation levels well below –20dB and achieve a simulated peak gain of 5.6 dBi at the highest frequency, with a compact cavity area of 0.56 λg^(2). The proposed antennas operate within the NR bands (n12, n18, n26), making them suitable for modern high-speed wireless communication systems. Moreover, the properties like multiband operation, compactness, high isolation, low loss, and low interference make the antenna favorable for the high-speed railway communication systems.
文摘In the current study the wear behavior of the ZK60/SiC composites reinforced by particles and whiskers in both as-cast and extruded conditions was examined.Furthermore,the wear behavior of the extruded samples along the extrusion direction and perpendicular to the extrusion direction was studied.The wear tests were performed at temperatures of 100,200,and 300℃under loads of 10,20,and 30 N.The results showed that the whisker-reinforced sample(5.8×10^(–4)g/[N.m])had higher wear resistance than the particle-reinforced sample(1.3×10^(–3)g/[N.m]).The lowest wear rate was observed for the extruded sample in the extrusion direction(3.53×10^(–4)g/[N.m]).It was also found that the wear rate increased by∼20%with increasing temperature,but in the ZK60/SiC_(w)sample,dynamic precipitation increased the wear resistance.The coefficient of friction was also found to increase with rising temperature,showing an increase of approximately 12.5%at a 10 N load and 20%at a 30 N load.Examination of the worn surfaces by scanning electron microscopy showed that the as-cast ZK60 alloy at 100℃had the oxidative-abrasive as the dominant mechanism.It was found that by extruding the sample,the strength of the sample increased and the mechanism changed to adhesive wear.In the ZK60/SiC_(p)composite,the viscoplastic wear mechanism was dominant.Although in the extruded sample the dominant mechanism changed to plastic deformation.As temperature increases,the viscoplastic wear mechanism became dominant again.In the as-cast ZK60/SiC_(w)composite,the abrasive wear mechanism changed to delamination with increasing temperature.By extruding the sample,the dominant mechanism changed to adhesive wear.Finally,dynamic precipitation induced by temperature caused an increase in the wear resistance.
文摘This article presents a compact crab-shaped reconfigurable antenna(CSRA)designed for 5G sub-6 GHz wireless applications. The antenna achieves enhanced gain in a miniaturized form factor by incorporating a hexagonal split-ring structure controlled via two radio frequency(RF) positive-intrinsicnegative(PIN) diodes(BAR64-02V). While the antenna is primarily designed to operate at 3.50 GHz for sub-6 GHz 5G applications, RF switching enables the CSRA to cover a broader frequency spectrum, including the S-band, X-band, and portions of the Ku-band. The proposed antenna offers several advantages: It is low-cost(fabricated on an FR-4 substrate), compact(achieving 64.07% size reduction compared to conventional designs), and features both frequency and gain reconfigurability through digitally controlled PIN diode switching. The reflection coefficients of the antenna, both without diodes and across all four switching states, were experimentally validated in the laboratory using a Keysight Field Fox microwave analyzer(N9916A, 14 GHz). The simulated radiation patterns and gain characteristics closely matched the measured values, demonstrating an excellent agreement. This study bridges the gap between traditional and next-generation antenna designs by offering a compact,cost-effective, and high-performance solution for multiband, reconfigurable wireless communication systems. The integration of double-split-ring resonators and dynamic reconfigurability makes the proposed antenna a strong candidate for various applications, including S-band and X-band systems, as well as the emerging lower 6G band(7.125 GHz–8.400 GHz).
基金the National Science Foundation under grant number CMMI-2339857.
文摘Friction stir processing(FSP)induces severe plastic deformation,generating intense strains and localized heating,which modifies the surface and enables the fabrication of magnesium(Mg)-based composites.This technique refines the microstructure of Mg alloys,enhancing mechanical properties—particularly ductility,a key limitation of these HCP alloys.This review addresses the underlying microstructural evolution during FSP of Mg alloys and Mg-matrix composites,including(i)grain refinement via continuous and discontinuous dynamic recrystallization(CDRX and DDRX),(ii)fragmentation and redistribution of secondary phases and intermetallics,(iii)transformation of low-and high-angle grain boundaries,and(iv)additional microstructural changes induced by external reinforcements.This review provides a comprehensive analysis of the strengthening mechanisms and their impact on the mechanical properties of FSP Mg alloys and Mgmatrix composites(MMCs).The paper examines the correlation between FSP processing parameters,microstructural evolution,and resulting mechanical properties.It critically highlights how the type of reinforcement and the dynamic recrystallization induced by friction stir processing influence grain boundary character and,consequently,the material’s strengthening response.It includes a comparative evaluation of yield stress,ultimate tensile strength,microhardness,elongation,and fractography for various FSP-treated Mg alloys and MMCs,including AZxx,WExx,ZExx,ZKxx,AMxx,AExx,and Mg-rare earth alloys.Additionally,the novelty of this review lies in its emphasis on connecting microstructural transformations to mechanical performance trends across different alloy systems and processing strategies,an aspect that has been underexplored in previous reviews.Recent advancements in FSP techniques and their implications for improving the performance of Mg-based materials are also discussed.
文摘This paper investigates the effects of material and dimension parameters on the frequency splitting,frequency drift,and quality factor(Q)of aluminium nitride(AlN)-on-n-doped/pure silicon(Si)microelectromechanical systems(MEMS)disk resonators through analysis and simulation.These parameters include the crystallographic orientation,dopant,substrate thickness,and temperature.The resonators operate in the elliptical,higher order,and flexural modes.The simulation results show that i)the turnover points of the resonators exist at 55°C,-50°C,40°C,and-10°C for n-doped silicon with the doping concentration of 2×1019 cm-3 and the Si thickness of 3.5μm,and these points are shifted with the substrate thickness and mode variations;ii)compared with pure Si,the modal-frequency splitting for n-doped Si is higher and increases from 5%to 10%for all studied modes;iii)Q of the resonators depends on the temperature and dopant.Therefore,the turnover,modal-frequency splitting,and Q of the resonators depend on the thickness and material of the substrate and the temperature.This work offers an analysis and design platform for high-performance MEMS gyroscopes as well as oscillators in terms of the temperature compensation by n-doped Si.
基金supported by CONACYT-Mexico,Lab Ex PERSYVAL-Lab(No.ANR-11-LABX-0025)Equipex ROBOTEX(No.ANR-10-EQPX-44-01)
文摘This paper proposes a simple solution for the stabilization of a mini-quadcopter carrying a 3DoF（degrees of freedom） manipulator robot in order to enhance its achievable workspace and application profile. Since the motion of the arm induces torques which degrade the stability of the system, in the present work, we consider the stabilization of both subsystems： the quadcopter and the robotic arm. The mathematical model of the system is based on quaternions. Likewise, an attitude control law consisting of a bounded quaternion-based feedback stabilizes the quadcopter to a desired attitude while the arm is evolving. The next stage is the translational dynamics which is simplified for control（nonlinear） design purposes. The aforementioned controllers are based on saturation functions whose stability is explicitly proved in the Lyapunov sense. Finally, experimental results and a statistical study validate the proposed control strategy.
文摘Solid oxide fuel cells based on doped cefia electrolytes offer operating temperatures of -600℃. During recent years much atten- tion was aimed at successful powder preparation with high sinter activity and high conductivity. The properties of ceria electrolyte are very sensitive to impurities introduced during powder and electrolyte fabrication. One of the most successful and commercially available processes for the production of clean powders is based on the addition of several percent metallic cations that will react with impurities and segregate into the triple points of grain boundaries. In this work the results obtained from doping of CGO20 by 2% Ca and prepared by different routes were presented. The way of introducing Ca seemed to play an important role.
文摘Naturalfibre(NFR)reinforced functional polymer composites are quickly becoming an indispensable sustainable material in the transportation industry because of their lightweight,lower cost in manufacture,and adaptability to a wide variety of goods.However,the major difficulties of using thesefibres are their existing poor dimensional stability and the extreme hydrophilicity.In assessing the mechanical properties(MP)of composites,the interfacial bonding(IB)happening between the NFR and the polymer matrix(PM)plays an incredibly significant role.When compared to NFR/syntheticfibre hybrid composites,hybrid composites(HC)made up of two separate NFR are less prevalent;yet,these hybrid composites also have the potential to be valuable materials in terms of environmental issues.A new dimension to theflexibility of composites reinforced with NFR is added by the cost-effective manufacture of hybrid composites utilising NFR.The purpose of this study is to offer an over-view of the keyfindings that were presented on hybrid composites.The emphasis was focused on the factors that influence the performance of the naturalfiber composites,diverse approaches to enhancing MP,physical,electri-cal,and thermal characteristics of the HC.HC study in polymer science gains interest for applications in con-struction and automotive industries.
文摘This paper proposes an adaptive nonlinear proportional-derivative(ANPD)controller for a two-wheeled self-balancing robot(TWSB)modeled by the Lagrange equation with external forces.The proposed control scheme is designed based on the combination of a nonlinear proportional-derivative(NPD)controller and a genetic algorithm,in which the proportional-derivative(PD)parameters are updated online based on the tracking error and the preset error threshold.In addition,the genetic algorithm is employed to adaptively select initial controller parameters,contributing to system stability and improved control accuracy.The proposed controller is basic in design yet simple to implement.The ANPD controller has the advantage of being computationally lightweight and providing high robustness against external forces.The stability of the closed-loop system is rigorously analyzed and verified using Lyapunov theory,providing theoretical assurance of its robustness.Simulations and experimental results show that the TWSB robot with the proposed ANPD controller achieves quick balance and tracks target values with very small errors,demonstrating the effectiveness and performance of the proposed controller.The proposed ANPD controller demonstrates significant improvements in balancing and tracking performance for two-wheeled self-balancing robots,which has great applicability in the field of robot control systems.This represents a promising solution for applications requiring precise and stable motion control under varying external conditions.
文摘Interference is a key factor in radar return misdetection.Strong interference might make it difficult to detect the signal or targets.When interference occurs in the sidelobes of the antenna pattern,Sidelobe Cancellation(SLC)and Sidelobe Blanking are two unique solutions to solve this problem(SLB).Aside from this approach,the probability of false alert and likelihood of detection are the most essential parameters in radar.The chance of a false alarm for any radar system should be minimal,and as a result,the probability of detection should be high.There are several interference cancellation strategies in the literature that are used to sustain consistent false alarms regardless of the clutter environment.With the necessity for interference cancellation methods and the constant false alarm rate(CFAR),the Maisel SLC algorithm has been modified to create a new algorithm for recognizing targets in the presence of severe interference.The received radar returns and interference are simulated as non-stationary in this approach,and side-lobe interference is cancelled using an adaptive algorithm.By comparing the performance of adaptive algorithms,simulation results are shown.In a severe clutter situation,the simulation results demonstrate a considerable increase in target recognition and signal to noise ratio when compared to the previous technique.
文摘Recently, many studies propose the use of ultra-wideband technology for passive and active radio frequency identification systems as well as for wireless sensor networks due to its numerous advantages. By harvesting these advantages of IR-UWB technology at the physical-layer design, this paper proposes that a cross layer architecture platform can be considered as a good integrator for different wireless short-ranges indoor protocols into a universal smart wireless-tagged architecture with new promising applications in cognitive radio for future applications. Adaptive transmission algorithms have been studied to show the trade-off between different specific QoS requirements, transmission rates and distances at the physical layer level and this type of dynamic optimization and reconfiguration leads to the cross-layer design proposal in the paper. Studies from both theoretical simulation and statistical indoor environments experiments are considered as a proof of concept for the proposed architecture.
文摘In this paper, a solution for electromagnetic compatibility guarantee based on the combination of metal shielding and circuit components distance estimation methods is presented. The electromagnetic noises generated from a working radio-electronic unit can expand into the space and act on other around radio-electronic units. An EMC guaranteed radio-electronic unit by the suitable technique method will not cause the electromagnetic noise to others. In opposition, it will not be under electromagnetic action from another one. Due to the power of electromagnetic noise, the metal shielding, distance estimation or other technique methods should be used to guarantee EMC. Every method has own advantage as so as weakness for detail radio-electronic unit, so it is necessary to choose a suitable method to guarantee EMC for them, the combination of metal shielding and distance estimation is a choice, for example. The proposed solution has been evaluated by using CST (Computer Simulation Technology) software and EMxpertEHX analyzer in oscillator circuit context. The simulated results on CST show that the proposed solution decreases the electromagnetic radiation about of 39.1 dB at frequency 500 MHz in comparison to results when nothing electromagnetic compatibility methods are not used. The experimental results on the oscillator circuit are presented. The electromagnetic radiation reduction of the oscillator circuit is about of (25 - 30) dB. In comparison to individual metal shielding and distance estimation methods, the effectiveness of the proposed solution for electromagnetic compatibility guarantee is significantly increased.
文摘This paper analyzes the possibility to discriminate between convective precipitation and stratiform precipitation. This study aims to improve the measurement of rainfall from teledetection data obtained both on the ground and in space. For this, two parameters, fractal dimension and fractal lacunarity, are considered. To calculate the fractal dimension, we use the approach of box-counting and show that the fractal dimension differs between convectives cells and stratiforms ones. And then the fractal lacunarity parameter is calculated by using the sliding boxes algorithm. The study for all the regions shows that precipitation cells can be described by different lacunarities whatever the scale of analysis. We deduce that the two parameters, fractal dimension and fractal lacunarity, can be used to classify precipitations in convective regime and stratiform regime.
基金This research is funded by the Industrial University of Ho Chi Minh City under code 20/1.6 DT01.
文摘In this paper,we propose a Two-Way Cognitive Relay Network(TWCRN)where the secondary users operate on an underlay mode to access the licensed bands.In the proposed protocols,two secondary sources transmit their data to a relay in the first time slot,and then the relay would forward the received information to both sources in the remaining time.Moreover,the relay is self-powered by harvesting energy from ambient Radio Frequency(RF)signals,using the Time Switching(TS)and the Power Switching(PS)method.This paper concentrates on eval-uating the performance of the secondary networks under the impact of hardware impairments and co-channel interference from the primary networks.In particular,based on the secondary transmitters'constraint power,we derive the closed-form expressions of the outage probability and the throughput over Rayleigh fading channels in two cases:TS and PS.We also investigate the energy efficiency issue and the locally optimal position of the relay to maximize the system throughput,which provides much information to install the relay location.Finally,our derivations are verified by Monte Carlo simulation.
文摘CIP （complex initial permeability） spectra of PF （polycrystalline ferrite） are studied both as intrinsic and extrinsic properties. In the former case, main steps of modeling, based on effects coming from polycrystal grain sizes distribution and defects, are described. The obtained relations work well in practice for PF with more or less normal MS （microstructure） and no size effects. Besides, fundamental connection between parameters of CIP and MS is found. Another case--PF with possible size effects （MnZn-ferrites） are studied experimentally for different sizes of cores, unveiling the dependence of phenomena on： dimensions of cross-section, number of turns, width of nonmagnetic gap.
文摘Currently, the market offers many visualization tools available to graphic designers, engineers, managers and academics working on maritime environments. The practice of visualization involves making and manipulating images that convey novel phenomena and ideas. Visual communication, together with virtual reality environments, is an emerging and rapidly evolving discipline. It brings great advantage over written word or voice alone, as visual sense is by far the most dominant component of human sensory perception. A new smart approach for modeling maritime vessels is described in this paper. Various ways of making modeling relevant for work within the field of maritime management, training and education are discussed.
文摘The paper discusses in a system view the security architecture of network layer of the Radio System for Monitoring and Acquisition of Data from Traffic Enforcement Cameras(in short RSMAD).The safety of this layer of the system is provided basing primarily on Virtual Private Networks(in short VPN).Two protocols have been used for their implementation:IPsec(in tunnel mode of ESP protocol)and L2TP.Applied cryptography data protection mechanisms,including the type and parameters of the VPNs have been selected on the basis of carried out tests and measurements,which results are presented and discussed in this paper.The study presents also detailed comparative analysis in terms of performance AES-128 and Triple-DES algorithms carried out in RSMAD.
文摘The authors＇ developed combined system model can be considered under the concept of next generation optical network （NGON） as a model for the future design of backbone networks. Such solution can be topical in the result of different telecom operators＇ optical networks convergence. In this case a necessity to transmit differently modulated signals over a single optical fiber even with different bit rates may occur. This research is performed with OptSim 5.2 simulation software that numerically solves nonlinear SchrOdinger equation. The authors have revealed the optimal parameter configuration for developed combined transmission systems and obtained in system＇s channels detected signals bit-error-rate （BER） correlation diagrams. They represent BER as a function from different system＇s parameters such as channel output power level, optical amplifier fixed output power level and system＇s channels allotment in C-band of ITU-T （Telecommunication Standardization Sector of the International Telecommunications Union） recommended spectral grid. As well as these obtained BER values were compared with the results for similar system, where instead of standard single mode fiber （according ITU-T Rec. G.652 D） optical signals are transmitted over non-zero dispersion shifted fiber （ITU-T Rec. G. 655）.
